p25 repeater and dsd+

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rjschilder

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Hi All,

Just for fun I threw together a repeater program in c# that works on Windows 7/8. It also sets the RTS/DTR (or both) pins high when transmitting the audio.

I wanted to make the repeater only transmit if a certain nac is decoded rather than setting audio levels. Since i'm not as smart as the people working on DSD+ or OP25, I decided to go another direction.

After some reading, I managed to grab the text output from DSD+ while it's decoding, search through each line as it comes in, and transmit based on the NAC it decodes :)

It's working very well! I'll post a youtube video tomorrow.

The other idea I had was to expand on the repeater and use it with NXDN / etc...
As long as there is some unique value output by DSD+, you should be able to use it as squelch.

I tested my repeater with a discriminator tapped pro-95 and the TX audio goes to the 6 pin mini din port of my yaesu ft-7800r.

Just thought i'd post for comments / suggestions. It's a work in progress.

-Ryan KC9GMY
 

Boatanchor

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You Dr Evil you :)

This sounds very intriguing....

Eyes light up, puts little finger in corner of mouth and utters "Mwa ha ha ha ha...."

This kind of ties in with my OP in this same forum, regarding using DSD+ to decode P25 from the Packet output port on the IC-208h.
Of course, if you can use a 'real' radio as the repeater's 'front end' you have the benefit of better bandpass filtering and sensitivity etc than using a scanner.

Look forward to updates.

Me thinks 2014 will usher in some awesome new hardware and software for SDR and Digi voice modes.

I don't think it will be long before someone uses one of the new wide band SDR TX/RX units to produce a complete digital repeater in a box.
Such a unit would simply require some off-board bandpass filtering on the RX and a PA on the TX, to bring the output power up to 25-50 watts.
 
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Boatanchor

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I presume you are simply feeding the raw RX audio from the scanner back into the TX audio port on the FT-7800R. Not ideal, but it will probably work as long as signals are strong enough and you don't need FEC on the repeater etc.
 

rjschilder

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Well yes and no to the audio feed.

I have the discriminator tapped audio to the line in on my laptop. It samples the audio at 48khz, throws it into a buffer with a 100ms delay, then outputs the audio at 48khz to the 9600bps pin of the ft-7800r through a custom cable I made. I'm using two Motorola Astro Sabers for testing and the output levels are actually pretty forgiving.

Still trying to get the short video uploaded to youtube. The youtube app on my gs4 apparently doesn't like me.
 

rjschilder

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So reading more of the posts in the DSD+ thread makes me a little more excited. I didn't know about the verbosity setting in DSD+. br0adband showed the following output with -v 3:

[E] Channel Group & User: tg=1231 src=10238

Makes me pretty sure that you could use NAC and talkgroup for squelch.

And i'm guessing using the color codes for DMR would be relatively straightforward. Although I have no DMR radios to test, if it uses 12.5khz bandwidth i'm relatively certain it could be repeated with the FT-7800R. I could be completely wrong though.

I'm assuming the same for RAN codes and NXDN. I haven't seen any posts yet with NXDN output from DSD+, but if it's there it can probably be used.
 

RonnieUSA

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So reading more of the posts in the DSD+ thread makes me a little more excited. I didn't know about the verbosity setting in DSD+. br0adband showed the following output with -v 3:

[E] Channel Group & User: tg=1231 src=10238

Makes me pretty sure that you could use NAC and talkgroup for squelch.

And i'm guessing using the color codes for DMR would be relatively straightforward. Although I have no DMR radios to test, if it uses 12.5khz bandwidth i'm relatively certain it could be repeated with the FT-7800R. I could be completely wrong though.

I'm assuming the same for RAN codes and NXDN. I haven't seen any posts yet with NXDN output from DSD+, but if it's there it can probably be used.
From my log for NXDN:

Sync:+NXDN48 CB DATA
Sync:+NXDN48 CB DATA
Sync:+NXDN48 CB VOICE
Sync:+NXDN48 CB VOICE
Sync:+NXDN48 CB VOICE
Sync:+NXDN48 CB VOICE
Sync:+NXDN48 CB VOICE
Sync:+NXDN48 CB VOICE
Sync:+NXDN48 CB VOICE
Sync:+NXDN48 CB VOICE
Sync:+NXDN48 CB VOICE
Sync:+NXDN48 CB VOICE
Sync:+NXDN48 CB VOICE
Sync:+NXDN48 CB VOICE
Sync:+NXDN48 CB VOICE
Sync:+NXDN48 CB VOICE e:1
Sync:+NXDN48 CB VOICE
Sync:+NXDN48 CB VOICE
Sync:+NXDN48 CB VOICE

There is No Ran Code in use for the frequency.
 

rjschilder

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Thanks! I must have missed that info. I'm guessing you could match the "+NXDN48 CB VOICE" string. I know there is a nxdn repeater in my area. I'll have to check it out later tonight and see if a RAN code shows up.
 

RonnieUSA

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Here is what I see listening to a NXDN 9600 system, no Ran Code on this one either.

Sync:+NXDN96 CB DATA
Sync:+NXDN96 CB VOICE
Sync:+NXDN96 CB DATA
Sync:+NXDN96 CB VOICE e:21
Sync:+NXDN96 CB DATA
Sync:+NXDN96 CB VOICE
Sync:+NXDN96 CB DATA
Sync:+NXDN96 CB VOICE
Sync:+NXDN96 CB DATA
Sync:+NXDN96 CB VOICE
Sync:+NXDN96 CB DATA
Sync:+NXDN96 CB VOICE e:1
Sync:+NXDN96 CB DATA
Sync:+NXDN96 CB VOICE
Sync:+NXDN96 CB DATA
 

rjschilder

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Thanks for the info! I posted a video to youtube yesterday but the quality on my phone doesn't translate over to youtube. everything that's perfectly in focus looks like garbage on youtube (even in 720p). I'm going to record a video with an actual camera tonight and post it.
 

oh6mwq_

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So, there is no data regeneration, did I got it right?

I've been looking for something like that to be used with these cheap Chinese dPRM (Zastone, Kirisun), but I guess DVD does not (yet) decode those.

Would be great to create a dPMR repeater on cheap...
 

rjschilder

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Hey all, this project got kicked waaaay to back burners. I just started tinkering with it again. I also have 4 DG9908/ZT9908 dpmr radios and would love to use it as a repeater. The only issue with the Luiton/Zastone dpmr radios is that the digital mode looks like it's locked to 6.25khz bandwidth and the radio I was using for TX can only go down to 12.5khz. There is an option for Wide/Narrow bandwidth, but I've put it on wide (assuming it would be 12.5khz) but SDRSharp showed a 6.25khz bandwidth no matter what. I'm guessing the dpmr radios wouldn't work properly if they receive a 12.5khz transmission (I could be very wrong as I haven't tried it yet). I'll polish it up a bit over the next week and release a beta version here.

-Ryan KC9GMY
 
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rjschilder

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@Ronenp - There is a textbox that says " Desired NAC" and a button next to it to set it.

@oh6mwq_ - There is no regeneration, correct. Although I don't think DSDPlus decodes dpmr. You may have to use the "audio threshold" feature to transmit if audio levels are above (or below) a certain level. When I was using the audio squelch instead of DSDPlus, I had a discriminator tapped scanner hooked up to my laptops line in. The problem I encountered was that the tapped audio always had noise, but the levels dropped once a signal was detected. Setting the audio threshold to transmit if the levels are below a certain level did the trick.

-Ryan KC9GMY
 

rjschilder

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Attached are sample screenshots of the current layout (may change it and add a menu bar at the top).

I have to add more options for nxdn/dmr color codes and such as well, didn't get around to it yet.

The top half of the image shows DSDPlus as squelch, and the current NAC being decoded (000 in this case as I wasn't decoding any data).

The bottom half shows the analog feature. You would use this for analog repeating or blind repeating of any digital data (or modes that aren't supported by DSDPlus - i.e. dpmr). I made some noise so I could show the program transmitting.

The RTS Status just shows if the RTS pin on the serial cable is +5v or not. It changes to 1(+5v) when transmitting.

The Transmit and Stop buttons are just for testing currently. They'll probably disappear.

I'll post more updates as the come in. Hopefully i'll put an alpha/beta version out sometime next week.

-Ryan KC9GMY
 

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rjschilder

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I'll try to get one up tomorrow night. I still have a bunch of stuff to implement for the dmr/nxdn stuff. p25 phase 1 with dsdplus works (as long as dsdplus.exe is in the root of C:\) and the analog works too. I literally haven't used this program to do digital except for p25p1 with the cable I made for the Yaesu FT-7800R plugged directly to the 9600bps data in port. Obviously if you try to do digital without a data jack (or some kind of TX mod that bypasses all the filtering) it won't work. Also, .NET 4.0 is required.

-Ryan KC9GMY
 

rjschilder

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and here is a new video I took this afternoon after changing some things around again. I tried it as a "simplex" repeater since I only have one of my astro sabers with me. I think i'd have to change some code around to get it to work properly this way, but it does work fine with the default 200ms delay which is what you'd want to use anyway.

new WinDigiPeater version - YouTube

-Ryan KC9GMY
 

rjschilder

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So after a little digging, I've discovered the latency really shouldn't go above 500 (hence some of the missing audio in the second video).

-Ryan KC9GMY
 
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